Artikelaktionen

6.2009

Efficient image blurring techniques based on the pyramid algorithm can be implemented on modern graphics
hardware; thus, image blurring with arbitrary blur width is possible in real time even for large images. However, pyramidal blurring methods do not achieve the image quality provided by convolution filters; in particular, the shape of the corresponding filter kernel
varies locally, which potentially results in objectionable rendering artifacts. In this work, a new analysis filter is designed that significantly reduces this variation for a particular pyramidal blurring technique. Moreover, the pyramidal blur algorithm is generalized to allow for a continuous variation of the blur width. Furthermore, an efficient implementation for programmable graphics hardware is presented. The proposed method is named “quasi-convolution pyramidal blurring” since the resulting effect is very close to image blurring based on a convolution filter for many applications.

This article begins with some recent considerations
about real-time music, inspired by the latest contribution
of French composer Philippe Manoury. Then,
through the case study of the scenic performance La
Traversée de la nuit, we analyse some perspectives for
designing an Informed Virtual Environment dedicated
to live show artistic domain.

This paper investigates the use of virtual reality (VR) technologies to facilitate the analysis of plant biological data in distinctive steps in the application pipeline. Reconstructed three-dimensional biological models (primary polygonal models) transferred to a virtual environment support scientists' collaborative exploration of biological datasets so that they obtain accurate analysis results and uncover information hidden in the data. Examples of the use of virtual reality in practice are provided and a complementary user study was performed.

Complementary to automatic extraction processes,
Virtual Reality technologies provide an adequate
framework to integrate human perception in the exploration
of large data sets. In such multisensory system,
thanks to intuitive interactions, a user can take advantage
of all his perceptual abilities in the exploration
task. In this context the haptic perception, coupled to
visual rendering, has been investigated for the last two
decades, with significant achievements. In this paper,
we present a survey related to exploitation of the haptic
feedback in exploration of large data sets. For each
haptic technique introduced, we describe its principles
and its effectiveness.

The integration of the auditory modality in virtual reality
environments is known to promote the sensations of
immersion and presence. However it is also known from
psychophysics studies that auditory-visual interaction
obey to complex rules and that multisensory conflicts
may disrupt the adhesion of the participant to the
presented virtual scene. It is thus important to measure the
accuracy of the auditory spatial cues reproduced by the
auditory display and their consistency with the spatial
visual cues. This study evaluates auditory localization
performances under various unimodal and auditory-visual
bimodal conditions in a virtual reality (VR) setup using a
stereoscopic display and binaural reproduction over
headphones in static conditions. The auditory localization
performances observed in the present study are in line
with those reported in real conditions, suggesting that VR
gives rise to consistent auditory and visual spatial
cues. These results validate the use of VR for future
psychophysics experiments with auditory and visual
stimuli. They also emphasize the importance of a
spatially accurate auditory and visual rendering for VR
setups.

The use of virtual reality as tool in the area of spatial
cognition raises the question of the quality of
learning transfer from a virtual to a real environment.
It is first necessary to determine with healthy
subjects, the cognitive aids that improve the quality
of transfer and the conditions required, especially
since virtual reality can be used as effective tool in
cognitive rehabilitation. The purpose of this study
was to investigate the influence of the exploration
mode of virtual environment (Passive vs. Active)
according to Route complexity (Simple vs. Complex)
on the quality of spatial knowledge transfer in three
spatial tasks.
Ninety subjects (45 men and 45 women)
participated. Spatial learning was evaluated by
Wayfinding, sketch-mapping and picture
classification tasks in the context of the Bordeaux
district. In the Wayfinding task, results indicated that
active learning in a Virtual Environment (VE)
increased the performances compared to the passive
learning condition, irrespective of the route
complexity factor. In the Sketch-mapping task, active
learning in a VE helped the subjects to transfer their
spatial knowledge from the VE to reality, but only
when the route was complex. In the Picture
classification task, active learning in a VE when the
route was complex did not help the subjects to
transfer their spatial knowledge. These results are
explained in terms of knowledge levels and
frame/strategy of reference [SW75, PL81, TH82].

This paper presents preliminary results about the use
of virtual characters, penile plethysmography and gaze
behaviour dynamics to assess deviant sexual preferences.
Pedophile patients’ responses are compared
to those of non-deviant subjects while they were immersed
with virtual characters depicting relevant sexual
features.

We present redirection techniques that support exploration
of large-scale virtual environments (VEs) by
means of real walking. We quantify to what degree
users can unknowingly be redirected in order to guide
them through VEs in which virtual paths differ from
the physical paths. We further introduce the concept of
dynamic passive haptics by which any number of virtual
objects can be mapped to real physical proxy props
having similar haptic properties (i. e., size, shape, and
surface structure), such that the user can sense these
virtual objects by touching their real world counterparts.
Dynamic passive haptics provides the user with
the illusion of interacting with a desired virtual object
by redirecting her to the corresponding proxy prop.
We describe the concepts of generic redirected walking
and dynamic passive haptics and present experiments
in which we have evaluated these concepts. Furthermore,
we discuss implications that have been derived
from a user study, and we present approaches
that derive physical paths which may vary from the
virtual counterparts.

Mixed Reality (MR) aims to link virtual entities with
the real world and has many applications such as military
and medical domains [JBL+00, NFB07]. In many
MR systems and more precisely in augmented scenes,
one needs the application to render the virtual part accurately
at the right time. To achieve this, such systems
acquire data related to the real world from a set
of sensors before rendering virtual entities. A suitable
system architecture should minimize the delays to
keep the overall system delay (also called end-to-end
latency) within the requirements for real-time performance.
In this context, we propose a compositional
modeling framework for MR software architectures in
order to specify, simulate and validate formally the
time constraints of such systems. Our approach is first
based on a functional decomposition of such systems
into generic components. The obtained elements as
well as their typical interactions give rise to generic
representations in terms of timed automata. A whole
system is then obtained as a composition of such defined components.
To write specifications, a textual language named
MIRELA (MIxed REality LAnguage) is proposed
along with the corresponding compilation tools. The
generated output contains timed automata in UPPAAL
format for simulation and verification of time constraints.
These automata may also be used to generate
source code skeletons for an implementation on a MR
platform.
The approach is illustrated first on a small example.
A realistic case study is also developed. It is modeled
by several timed automata synchronizing through
channels and including a large number of time constraints.
Both systems have been simulated in UPPAAL
and checked against the required behavioral
properties.